This proposal represents the first totally integrated approach to developing a suitable mechanical circulatory assist device for use in the pediatric patient. Despite technical advances in pediatric cardiac surgery, profound refractory heart failure following technically successful correction of congenital lesions remains a significant cause of mortality. The inability to wean an infant from cardiopulmonary bypass or improve a low-output syndrome in the immediate postoperative period with medical therapy is fatal since intra-aortic balloon pumping is not particularly effective in this age group. Safe effective cardiac assist devices are currently available for use in small patients. The safety and efficacy of ventricular assist pumping has been established in the laboratory and in the clinical setting for treating adult patients with postcardiotomy cardiogenic shock. These results suggest that ventricular assist pumping may have a role in the pediatric age group postcardiotomy cardiogenic shock. Such use may be expected to significantly reduce mortality in these patients. Through a collaborative effort, we propose modification of the current angle port pneumatically driven ventricular assist pump and cannulas developed at The Pennsylvania State University for this application. A scaled down 10cc stroke volume device capable of supporting an infant's systemic and/or pulmonary circulation will be fabricated by 3M/Sarns Inc., and tested in vitro via mock circulation and flow visualization studies at The Pennsylvania State University. Short term animal studies utilizing infant goats (The Pennsylvania State University) and dogs and sheep (Mayo Foundation) are proposed to test the safety and efficacy in vivo. Following satisfactory completion of animal studies and appropriate FDA approval, we propose human application at The Milton S. Hershey Medical Center and at the Mayo Foundation in pediatric patients who following technically successful correction of a congenital heart lesion cannot be separated from cardiopulmonary bypass or who develop low cardiac output syndrome in the immediate postoperative period. The ability of assist pumping to temporarily support the systemic and/or pulmonary circulation while allowing time for myocardial recovery and improved patient survival will be evaluated. The time course of recovery of ventricular function and physiologic effects of assist pumping will be studied via standard laboratory and hemodynamic techniques.